Contractile activity of the prostate at ejaculation: an electrophysiologic study.

OBJECTIVES To investigate the hypothesis that the prostate contracts at ejaculation to push its secretions into the urethra. Although it has been mentioned that the prostate contracts at ejaculation, a report of this finding could not be traced in published studies. METHODS The electromyographic activity of 8 canine prostates was recorded by applying an electrode to the prostate. The prostatic urethral pressure was simultaneously measured by means of a manometric catheter. The prostatic electromyographic and urethral pressures were recorded at rest and on ejaculation by penile electrovibration. RESULTS The prostatic slow waves (SWs) and action potentials (APs), as well as the urethral pressure at rest, showed a significant increase during the ejaculatory bouts (P < 0.05 and P < 0.05, respectively). The SWs, APs, and pressure increase occurred simultaneously with each bout of ejaculatory spurt, which occurred at mean intervals of 1.1 +/- 0.02 seconds and a number of 4.6 +/- 1.2 bouts. CONCLUSIONS The electric waves discharged from the prostate at rest seemed to produce prostatic contractions, which cause prostatic urethral pressure increases. At ejaculation, the intermittent increase of the wave variables and urethral pressure coincided with the ejaculatory spurts, apparently denoting intermittent prostatic smooth muscle contractions. These contractions seem to squeeze the prostatic secretions into the prostatic urethra.